1. Field of the Invention
The invention relates generally to methods and devices for operating siding sleeve devices used in subterranean wellbores and the like.
2. Description of the Related Art
Sliding sleeve valve devices are well known and widely used in downhole hydrocarbon production. Typically, these devices are made up of an outer tubular housing that defines an axial flowbore within. One or more radial fluid transmission ports are disposed through the outer housing. The outer tubular housing contains an inner sleeve member that is shiftable (typically axially) within the housing. The inner sleeve member also presents a radial fluid port through its body, which is selectively aligned with the fluid transmission port(s) in the housing as the sleeve is shifted within the housing. Typically also, there are annular seal rings located on either axial side of the fluid transmission port(s) to prevent fluid from flowing between the housing and sleeve member.
Operational problems arise where there is a significant pressure differential between the interior flowbore and the surrounding wellbore. If this situation exists when the sleeve valve is being moved from a closed to an open position, or an open to a closed position, the seal rings are especially vulnerable to high pressure fluids passing through the aligned fluid ports. As the valve fluid ports are slidingly moved with respect to each other, there is a point at which the port are partially aligned and fluid is forced through a very small area opening. The differential fluid pressure placed upon the seal rings at this point is quite high. The seal rings can be blown out or otherwise damaged during the process of opening or closing the sleeve valve. Damage to the seal rings can seriously degrade or eliminate the ability of the sleeve valve to close off fluid flow into or out of the flowbore.
At times, conditions develop within the wellbore wherein a sleeve valve must be opened or closed under differential pressure situations that are much greater than originally planned. A valve that is designed to open against a differential fluid pressure of, for example, 1,500 psi may be moved into a lower portion of the wellbore wherein differential pressures exceed 5,000 psi. In such a situation, operating the valve between open and closed positions would be inadvisable and likely destroy the ability of the valve to function properly thereafter.
The present invention addresses the problems of the prior art.